Case studyMild encephalopathy with reversible splenial lesion: An important differential of encephalitis
Introduction
Mild encephalopathy with a reversible splenial lesion (MERS) is a clinico-radiological syndrome which was first proposed by Tada et al.1 in 2004 and further expanded by Takanashi et al.2 It is typically characterized by a prodromal illness consisting of fever, cough, vomiting or diarrhoea, followed 1–7 days later by encephalopathy. Common neurological symptoms include behavioural change, altered consciousness and seizures.2 These symptoms resolve rapidly over days without treatment and there is typically complete neurological recovery. Magnetic resonance imaging (MRI) during the acute episode reveals a lesion in the splenium of the corpus callosum, sometimes also extending to other areas of the corpus callosum and adjacent parenchymal white matter. The lesions are typically symmetrical and show T2 hyperintensity with corresponding diffusion restriction and no contrast enhancement. These changes resolve completely or near completely on follow up imaging within days to weeks.1, 2
The underlying pathogenesis of MERS is unknown. Takanashi et al. proposed an infectious trigger in their case series of 54 Japanese patients with MERS.2 A recent systematic review by Garcia-Monco et al. revealed multiple other potential causes of reversible splenial lesions, however infectious related MERS remains the most common cause of reversible splenial lesions in childhood.3
MERS is a condition that has largely been described in case reports and case series from East Asia and Japan. To our knowledge, there have been less than 10 published cases of MERS occurring children outside of Japan and East Asia.4, 5, 6, 7, 8 In this study, we describe the findings of seven Caucasian Australian children who presented with MERS over a 3 year time period, demonstrating this to be an important clinical entity outside of East Asia.
Section snippets
Methods
Patients with possible MERS were identified by reviewing the neurology departmental database of inpatient consultations and by directly contacting the neurologists at the Children's hospital at Westmead. We performed a full retrospective chart review of the patients referred for the study. We collected information about ethnicity, past medical history, clinical features, medications, treatment, investigations and outcome. We reviewed all neuro-imaging in conjunction with the paediatric
Results
Seven patients presenting over a 3-year period (2010–2013) were included. All patients were Caucasian with median age of five years (range 3–9). Three patients had a pre-existing medical problems (Table 1). The other children were previously well with normal neurodevelopment.
All seven patients had non-specific symptoms of acute infection prior to encephalopathy onset: fever (n = 7), vomiting (n = 5), cough/coryza (n = 4), abdominal pain (n = 2), headache (n = 2) and diarrhoea (n = 1). One child
Discussion
We report seven cases of MERS in Caucasian Australian children to emphasise the existence of this syndrome outside of East Asia, and increase awareness of this clinical entity as a diagnosis to consider in a child presenting with acute encephalopathy. The clinical findings of our patients were similar to previously reported MERS patients, except that seizures only occurred in one of the seven patients, whereas it has been reported to occur in 33% of a large case series of Japanese patients.2
Conflict of interest
No author reports a conflict of interest.
Acknowledgements
We would like to thank participants of the childhood encephalitis surveillance studies ongoing at the Children's Hospital at Westmead.
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2020, Journal of Clinical NeuroscienceCitation Excerpt :Mild encephalopathy with reversible splenium lesion (MERS) is a clinico-radiographical condition that is characterized by a reversible lesion isolated to the corpus collosum on magnetic resonance imaging (MRI) [10]. Patients with MERS typically present with fever and associated encephalopathy and lethargy [10]. Other neurological manifestations that have been reported are seizures and behavioral changes [10].